Description

The behavior of Marbled Murrelets (Brachyramphus marmoratus) at sea while foraging for small fish and invertebrates is poorly known. This murrelet forages by pursuit diving in relatively shallow waters, usually between 20 and 80 meters in depth. We have also observed it diving in waters less than 1 meter and more than 100 meters deep. The majority of birds are found as pairs or as singles in a band about 300 to 2000 meters from shore. Pairs tend to dive simultaneously when foraging, and we suggest that pairing has some benefit to foraging efficiency. At times they are in small flocks and in aggregations. Larger aggregations are found in the northern part of its range, probably due to the denser population. Foraging dive times averaged about 16 seconds. Murrelets generally forage during the day, and are most actively in the morning and late afternoon hours. Some foraging occurs at night. Vocalizations during foraging occur after individuals of a pair surface apart from each other. The majority of the birds’ surface time is spent loafing, preening, and wing stretching. We feel that adults holding fish are usually about to depart inland to feed a young, and are potentially a very useful measure of reproductive rate. Murrelets are not generally associated with interspecific feeding flocks, except in the northern part of its range.